Overload device



`luly 10, 1923. 1,461,370 c. H. RIPPL.

OVERLOAD DEVICE Filed Dec. 14, 1921 2 Sheets-Sheet l .fn/VENTO@ WI-rrvesn July 10, 1923. 1,461,370 C. H. RIPPL OVERLOAD DEVI CE Filed Dec. 14, 1921 2 Sheets-Sheet 2 Patented July 10, 1923.

UNITED STATES PATENT OFFICE.

CHARLES H. RIPPL, OF CLEVELAND, OHIO, ASSIGNOR TO THE ELECTRIC CONTROLLER MANUFACTURING COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

OVERLOAD DEVICE.

Application led December 14, 1921. Serial No. 522,231.

To all lwhom 'it may concern.'

Be it known that I, CHARLES H. .RIrrn a citizen of the United States, resldmg at Cleveland, in the county of Cuyahoga andv State of Ohio, have invented new and usei ful Improvements in Overload Devlces, of

whichA the following is a speciiication.

My invention relates to overload devices for electric systems which employ one or more heat-expansive devices to cause 'the source of current supply to be disconnected from an electric-motor or other translating device upon the existence of overloads having certain characteris'tics.

It is the principal object of this invention to provide an induction or other motor or its equivalent with one or more heat-expansive devices which will permit a normal heavy overload, such as occurs during the starting of an induction motor, for example,

` to persist for a deinite period, but' will cause the current supply to be cut off it the overload persists beyond that period; which will interrupt the current'supply immediately upon the occurrence of an abnormally large overload which might destroy or damage the motor or its equivalent; and which will interrupt the current supply upon the persistence of smaller overloads for periods whose lengt-hs depend upon the sizes of the overloads.

While this invention may be used with various types of electrical systems and devices, I have shown it as a modification in the system shown and described in the application of Homer E. Frost, Serial Number 488,990, filed August 1, 1921.

On the accompanying drawings, Fig. 1 is a side elevation of an overload device embodying the principles of my invention; Fig. 2, a bottom plan view of Fig. 1 with some of the parts omitted; Fig. 3, a view of the upper part of Fig. 1; Fig. 4, a sectional detail showing the rear member of the tripping device; Fig. 5, an enlarged detail looking at the right hand of Fig. 3; Fig. 6, a detail of the tripping mechanism in the position in which it is when the circuit is open; Fig. 7, a diagrammatic view of the circuit which may accompany my device; and Fig. 8, a diagram showing the eiliciency of my invention.

On the drawings 1 indicates an insulating base composed of slate, for example. 2 and 3 are heat-expansive wires severally connected at one end to the metal blocks 6 and 7 seated in the respective forks 4 and 5 Sccured to the base 1. The blocks are adjustably held in the forks by the nuts 8 and9 which bear on the outside edges of the forks. The remaining ends of the wires 2 and 3 are insulated from each other and respectively connected to the shorter ends of the levers 10 and 11 which are insulated from the wires and pivoted on the in and pivot l2 supported by the base 1. IFach lever is composed of an outer member 13 and an inner member 14 connected together at their upper ends by a pin l5. To the pin 15 the wires 2 and 3 are respectively attached. The levers 10 and 11 have inwardly projecting tripping fingers 16 and 17, respectively, formed by projections from their members 13 and 14. The projections of each pair of members are connected together by a spacing pin 18. The members 13 of the levers have below the projections 16 and 17 holes to loosely receive the end necks 19 of the equalizing pin or bar 20, which has central between the necks 19 the neck 2l to which one end of the operating spring 22 is attached, the other end thereof being connected to the post 23 secured to the base 1. 24 is a switch-tripping lever comprising the back member 25 and the front member 26, both pivoted on the pivot 27 secured to the base 1. The members are connected together by the pin 28. The lower 'end of the member 25 is engaged by the spacing pin 18 oi' the lever 11., and the lower end ofthe lever member 26 is engaged by the spacing pin 18 of the lever 10, as shown best in Fi 5. A switch-reset spring 29 tends to keep tie lower ends of the members 25 and 26 in contact with the fingers 16 and 17. The upper end of 95 the member 25 has the 'fork members 30 and 31, between which is the fixed post 32 acting as a stop for the Jfork members and as a support for the bell crank lever 33 pivoted on the outer end thereof, and having the arms 34 and 35. An overthrow spring 36 connects the arm 34 to the upper end of the member 26, the spring lying to 'the right of the pivot post 32 when the arm 35 is horizontal. The arm 35 is connected by the link 105 o' insulating material 36 to the free end of the lever 37 carried bythe pivot 38 below the link. The pivot 39, which connects the link to the lever 37, also carries the rocking contact 40, having its upper end'arranged to engage the fixed contact or post 41 when the link and the arm (which are togglemembers) are in a substantially straight line, as shown on Fig. 1. The lower end of the lever is connected to the spring 42 which allows the contact 40 to have a wiping action on the contact 41. The contact 41 is connected by the lead 45 to the terminal 46. The lead 43 connects 38 to 44.

The end of the wire 2 connected to the block 6 is connected by the wire.48 to the terminal 57 on the base, and the end thereof connected to the lever 10 is electrically connected lto one end of the coil 77 which is wrapped around the wire 2. Between the wire 2 and the coil 77 is a tube or sheath 78 composed of asbestos or other material. The remaining end of the coil is connected to the terminal 56 by the wire 47. Similarly, the wire 3 is provided with the coil 79 which is separated from the wire 3 by the tube or sheath 80, the ends of the wire and coil not joined to each other being connected to the terminals 60 and 59 by the wires 51 and 50, respectively.

Referring now to Fig. 7, the terminals 56 and 59 are connected to the two terminals 63 and 64 of the alternating current motor 65. The terminals 57 and 60 are connected to the movable switch members 66 and 67 of the switch 68. The third motor terminal 69 is connected to the movable switch member 70. The said switch members are pivotally connected to the operating bar 71, actuated. by the switch-operating winding 72 t0 close the switch members 66, 67 and 70 on their fixed contacts 73, 74 and 75, and actuated by the spring 76 to open the said switch members when the winding 72 is de-energized. The contacts 73, 74 and 75 are connected to the source of alternating current supply by the supply wires 7 7, 7 8 and 79. The winding 72 is connected in the circuit of the neutral contact 75 and in one of the outer wires, as 77, though the hand switch 80 and the parts 37, 38, 40 and 41, as shown in n Fig. 8 the equalizing pin 2O is represented as applied directly to the wires 2 and 3 at the polnts a and b, these indicating the position of the equalizer when the wires 2 and 3 are cold. The corresponding point of application of the spring 22 is indicated by the letter c. a and b indicate the position of the equalizing pin 2O when both the wires 2 and 3 become heated and stretch equally under the pull of the spring 22 until the levers 10 and 11 jointly cause the tripping lever 24 to open the contacts 40 and 41. When the equalizing pin 20 takes the position a-b, the point of application of the spring 22 is at' c. If the circuit of one of t e Wires, as 2, has been interrupted, the

marmo equalizing pin will take the diagonal position w--Z the point of application of the spring 22 being at c.

Let it be assumed that the spring 22 exerts a pull of 15 lbs. at the point c. Then the pull thereof on the points a and b will be 7.5 lbs. each. Assume that, when the equalizing pin is at the position a--b, the ypull of the spring has been reduced to 6 lbs. Then the pull at a and Z9 will be reduced to 3 lbs. each. If the wire 2 is out of circuit, the point a will remain stationary while the point b will move to b', the point c moving to c, at which point the spring exerts a pull of only 10.5 lbs. divided between the points a and b. rIhe pull at b will be somewhat in excess of 5.25 lbs., owin to the movement of the point c of the app ication of the spring 22 slightly toward the point 7). The necks of theequalizing pin 2O cause a readjustment of the points of application when the bar moves from the position a-b to the diagonal position 1f-b', so that the power of the spring on the point b is greater than on the point a. Thus, the spring which exerts a pull of only 3 lbs. on each wire when both wires are equally heated, exerts a pull of more than 5.25 lbs. on one heated wire, as 3, when the other wire, as 2, is open circuited. This means that the heated wire 3 is stretched sufiiciently to trip the switch contact 40 before the wire 3 is heated to such a high temperature as would have been re uired if both wires were heated equally. i separate springs were employed, each pulling 7.5 lbs. at the points a and 6, and the wire 2 was out of circuit, the spring acting on the oint a would still exert a pull 067.5 lbs. w iile the spring acting on the point b would exert a pull of 3 lbs., a loss of 2.25 lbs. over the pull exerted at the point b when only one spring is pulling at the point c.

Referring particularly to Fig. 7, if the switch 80 is closed, the single phase current in the winding 72 will cause the switches 66, 67 and 70 to engage the contacts 73, 74 and 75, thereby connecting the neutral wire 79 to the motor terminal 69, while the outer wires 77 and 78 are connected to the remaining motor terminals 63 and 64 through the windings 77 and 79 and the two wires 2 and 3. When the contacts 40 and 41 are opened, the winding 72 is (le-energized, permitting the spring 76 to open the switches 66, 67 and 70 and cause the motor 65 to stop.

As the upper end of the lever 24 is moved to the left in Fig. 1 by the action of the lever 10 or the lever 11 or both, the spring 36 passes from the right side of the ulcrum 32 of the lever 33 to the left side thereof,

thereby causing the latter to move quickly from the position shown in Fig. 1 to that shown in-F ig. 6 where the toggle members 35, 36, have pulled the lever 37 'to the left enough to open the contacts 40 and 41..

So far the operation of my invention has been given without reference to the functions of the coils 77 and 79 and the tubes or sheaths 78 and 80. The wires 2 and 3 have larger cross-areas than the wires of which the coils are made. The' wires 2 and 3 are affected in their degrees or amounts of expansion by heat due to current therein and also b heat transmitted from the coils throug the tubes 78 and 80, if the latter are employed,l The difference between the crossareas of the wires 2 and 3 and cross-arcas of the wires in the coils 77 and 79 may be compensated in whole or part by makinothe wires 2 and 3 of a material havin a ower s cic resistance than the wires o the coils. 'lllie time required for the coils to heat the wires 2 and 3 to a definite temperature is controlled by the thickness of the wall of the tubes 78 and 80 andthe materials of which the are made. To increase the time element t e walls of the tubes are made thicker or of a poorer conductor of heat.

In starting an induction motor of the squirrel-cage type, it may be necessary to draw from three to tive times full load current for three to ten seconds. The wires 2 and 3 are selected so they will not expand enough to cause the contacts 40 and 41 to be opened under these conditions. The wires of the coils are selected so that they will not be damaged and the tubes 78 and 8() are selected so that they will not transmit enough heat to expand the wires 2 and 3 to the trip` ping point. If the startin current shou d rsist morethan .the pre etermined numr of seconds, the wires 2 and 3 will become heated by the coils so as to cause the contacts 40 and 41 to open. It is clear that even with smaller overloads than the said normal startin overloads, the coils will, if suliicient time as elapsed, heat the wires .2 and 3 suiciently to cause the supply circuit to be opened. As the tubes 78 and 80 retard the flow of heat to the wires 2 and 3, the coils and the wires 2 and 3 would burn out on a suiciently high current, if provision was not made agalnst it. This provision consists in the present instance in making the wires 2 and 3 sufficiently small to cause them to expand enough by the current therein to trip. the circuit breaker before the wires of the coils, or the wires can be damaged. A

It is manifestlyimpossible to state the proportionate correlation of the three functional elements, the expansive wires, the enveloping coils and the intermediate tubes or sheaths. Those skilled in the art can readily determine the roper characteristics of these elements for. tlrie particular installations desired.

l I have shown my invention in connection 'of Dec., 1921.

with a three-wire alternating current system, but it is evident that it is applicable to other multiphase systems, and to various other arrangements.

While I have described the expansive wire as having a larger cross-area or a higher specilc resistance than the wire of the coil, I may for some purposes make the expansive wire with a smaller cross-area or a flower specific resistance than the wire of the coil.

1. In an overload device for an electric circuit, a switch for controlling the circuit, an expansive wire electrically connected to the circuit for controlling the switch, a coil electrically connected to the circuit and arranged to transmit heat to the wire, the thermal capacity per linear unit of the expansive wire and of the wire of the coil being so proportioned that, when current above a predetermined value traverses the expansive wire and coil, the former will efect the operation of the switch without overheating the coil and, when current above a predetermined lower value traverses the expansive wire and coil, the coil will transmit suiicient heat to the expansive wire to effect the operation of the switch before the coil becomes overheated.

2. In an overload device for an electric circuit, a switch for controlling the circuit, an expansive wire electrically connected to the circuit for controlling the switch, a coil electrically connected to the circuit and arranged 'to transmit heat to the wire, an insulation between the expansive wire and the coil, the insulation having such thickness, and the thermal capacity r linear unit of the expansive wire and oethe wire of the coil being so proportioned that, when current above a predetermined value traverses the expansive wire and coil, the former will effect the operation of the switch without overheating the coil and, when current above a predetermined lower value traverses the expansive wire and coil, the coil will transmit suiiicient heat to the expansive Wire to effect the operation of the switch before the coil becomes overheated.

3. In a circuit, a heat expansive wire for controlling the circuit, and a heating coil connected thereto and arranged toheat the wire, the thermal capacities per linear unit of the expansive wire and the conductor of the coil being so proportioned that the expansionof the wire effective to control the circuit is due to the heat transmitted to the wire by the coil when the current in the circuit exceeds a predetermined valuel and is due to the heating of the wire by the current therein when the current exceeds a second predetermined value.

Signed at Cleveland, Ohio, this 7th day CHARLES H. RIPPL. 

